Fingerprint sensing and matching is a reliable and widely used technique for personal identification or verification. In particular, a common approach to fingerprint identification involves scanning a sample fingerprint or an image thereof and storing the image and/or unique characteristics of the fingerprint image. The characteristics of a sample fingerprint may be compared to information for reference fingerprints already in a database to determine proper identification of a person, such as for verification purposes.
A particularly advantageous approach to fingerprint sensing is disclosed in U.S. Pat. No. 5,963,679 to Setlak et al. and assigned to the assignee of the present invention. The fingerprint sensor is an integrated circuit sensor that drives the user's finger with an electric field signal and senses the electric field with an array of electric field sensing pixels on the integrated circuit substrate. Such sensors are used to control access for many different types of electronic devices such as computers, cell phones, personal digital assistants (PDA's), and the like. In particular, fingerprint sensors are used because they may have a small footprint, are relatively easy for a user to use, and they provide reasonable authentication capabilities.
U.S. Published Patent Application No. 2005/0089203 also to Setlak and assigned to the assignee of the present invention discloses an integrated circuit biometric sensor that may sense multiple biometrics of the user, and that is also adapted to either a static placement sensor or a slide finger sensor. A slide finger sensor includes a smaller sensing surface over which the user's finger is slid. The images collected during the sliding process may be collected for matching, such as for authentication, or may be used for navigation, for example.
For example, U.S. Published Application No. 2003/0156744 to Hashimoto also discloses a slide fingerprint sensor system that uses a portion of the sensing array to determine if a finger is present on the sensor. The system also includes a unit connected to the fingerprint sensor for preventing image overlap, and a unit for determining the speed at which a finger is slid over the fingerprint sensor. Similarly, U.S. Published Application No. 2003/0194114 to Mitsuyu et al. discloses a slide fingerprint sensor having a unit connected to the fingerprint sensor for determining the speed at which a finger is slid over the fingerprint sensor.
U.S. Published Application No. 2002/0012455 to Benckert also discloses a slide fingerprint sensor system that can determine the speed at which a finger is slid across the fingerprint sensor. The system further includes a controller connected to the fingerprint sensor for correlating subareas of fingerprint data generated by the fingerprint sensor.
U.S. Published Application No. 2003/0002718 to Hamid discloses a slide fingerprint sensor including a processor for cropping slices of image data into a single image. The processor is connected to a data input/output port for providing communications with a fingerprint correlation system.
U.S. Published Application No. 2003/0123714 to O'Gorman et al. discloses a slide fingerprint sensor system including a processor for removing overlap in fingerprint images generated by the system. The processor may be integrated onto the sensor or alternatively, the processor may be remote from the sensor.
Unfortunately, conventional slide or swipe fingerprint sensors may consume a large amount of power because of the computational demands required by such systems. As biometric access systems become incorporated into a greater number and variety of portable electronic devices, this power demand becomes a problem for the limited battery power sources typically carried by the portable electronic devices.